In prior methods from the market for commercial vehicles, e.g., trucks driven by an internal combustion engine, the user of the vehicle may express a certain desire for power by operating an accelerator pedal. At a certain rotational speed, this power request corresponds to a certain propulsion torque at the output of a transmission of the internal combustion engine, which drives the commercial vehicle. On the basis of the transmission ratio, a clutch torque which must be available at the input of the transmission is calculated from the desired transmission output torque. Taking into account the internal friction of the internal combustion engine and the power tapped off by auxiliary units such as the fuel pump, the air conditioning system and so forth, the indicated torque or internal torque which must be generated by the combustion of fuel to supply the propulsion torque desired by the user is finally determined. This internal torque is essentially proportional to the amount of fuel injected, depending on the type of internal combustion engine and the operating state.
To protect the operating brake (e.g., disk brakes) acting on the driving wheels, there is usually an additional “engine brake” on commercial vehicles. With this engine brake, a negative propulsion torque may be generated by the engine, e.g., for prolonged downhill traveling.
Such an engine brake is usually operated by the driver via a two-step switch which turns the engine brake either on or off. However, automatic operation by a cruise control system which maintains a constant driving speed of the commercial vehicle without any intervention on the part of the driver is also possible.